<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			#yy{
				border: 1px solid red;
				height: 800px;
				width: 800px;
				position: relative;
			}
			#y2{
				border: 1px solid blue;
				width: 400px;
				height: 400px;
				left: 200px;
				top:200px;
				position: absolute;
			}
		</style>
	</head>
	<body>
		  <div id="yy">
		  	bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
		  	<div id="y2">我我我</div>
		  </div>
	</body>
</html>
